Liquid crystal display elements or touch panels (touch sensors) are used in display apparatuses of large electronic apparatuses such as personal computers and television sets; small electronic apparatuses such as car navigation systems, mobile phones, and electronic dictionaries; and OA and FA apparatuses. These liquid crystal display elements or touch panels are provided with electrodes composed of transparent conductive electrode materials. ITO (indium-tin-oxide), indium oxide, tin oxide or the like is known as a transparent conductive electrode material, and these materials exhibit high visible light transmittance, and therefore are predominant as a transparent electrode material of substrates for liquid crystal display elements and the like.
Various types of touch panels have already been practically used, and recently, use of capacitive touch panels has been developed. In the capacitive touch panels, when a fingertip as a conductor gets in touch with a touch input screen, capacitive coupling occurs between the fingertip and the conductive film to form a capacitor. Accordingly, the capacitive touch panel senses a change in charge in the touch position of the fingertip to detect its coordinate.
In particular, because projected capacitive touch panels can detect the fingertip at several points, the projected capacitive touch panels have excellent operability enabling performance of complex instructions, according to such excellent operability, the projected capacitive touch panels has been developed for using as input devices on display surfaces in apparatuses having small display devices, such as mobile phones and portable music players.
In general, in the projected capacitive touch panels, a plurality of X electrodes and a plurality of Y electrodes orthogonal to the X electrodes are formed into a two-layer structure to express a two-dimensional coordinate of an X-axis and a Y-axis, and as the constituent material for these electrodes, ITO (Indium-Tin-Oxide) is used.
The frame regions of the touch panels are regions in which the touch location cannot be detected. Therefore, a reduction in the area of such frame region is an important factor to increase the product value. The frame region requires metal wiring to transmit the detection signal of the touch location. The width of the metal wiring needs to be reduced to reduce the frame area. In general, copper is used for the metal wiring because the conductivity of ITO is not sufficiently high.
However, in the touch panels as described above, corrosive components such as moisture and salt may intrude inward from the sensing regions when the touch panels are in contact with the fingertip. If corrosive components intrude into the touch panels, the metal wiring may corrode to increase the electric resistance between the electrodes and driving circuits or cause disconnection.
As a method of disposing a resist film at a necessary portion in order to prevent the corrosion of metal wiring, there is a known method in which a photosensitive layer composed of a photosensitive resin composition is provided on a predetermined base material, and this photosensitive layer is exposed and developed (for example, Patent Literature 1 below).